IRM changes announced

The Royal Ocean Racing Club has announced the following IRM changes for 2006. James Dadd IRM chief measurer reports

Following on from the introduction of the VCG factor for 2005 we have seen increased interest in boat on boat racing using IRM as the base platform. The introduction of the VCG factor has allowed us to look into the original surrogate controllers of deep VCG and minimal hull form stability. In general however, the changes made this year are minimal, to try and ensure some stability for the IRM fleet in the coming 12 months.

1. Beam Factor (BF)

With the introduction of the VCGF we eased the effects of this for narrow designs for 2005. The discouragement is now removed for 2006.

2. Weigh Factor (WF)

Again we have reduced the discouragement for high displacement designs. There is still an encouragement for new designs to be of relatively light displacement, but with more designs wishing to compete in IRM it is felt that the strong original discouragement is not necessary for the fleet at large.

3. Length Factor (TCMb)

Whilst it is difficult to study the actual effects of the length factor with the majority of IRM racing being in relatively small size bands and on short windward/leeward courses, it is recognised that there may still be some leaning towards the larger boats. The base TCM is therefore adjusted slightly to compensate for this.

The net result of these changes is demonstrated in the table below:Please note, this table shows general trends only, ratings may vary depending on measured data.

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